This is a typical forms error which will come when the pll library files are not found in the location set in the PATH environment variable. Ensure your library is found in the path set in your FORMS60_PATH environment variable.

In regedit, go to HKEY_LOCAL_MACHINE -> SOFTWARE -> ORACLE. Find the subdirectory where FORMS90_PATH is (mine is HOME2). Make sure that the directory where Your library is, is included in the path